This invention generally relates to optical diagnosis and measurements of the eye, and in particular embodiments provides devices, systems, and methods for measuring the changes in pupil position, location, and the like with changes in distance and/or other viewing conditions.
Presbyopia is a condition that affects the accommodation properties of the eye. As objects move closer to a young, properly functioning eye, ciliary muscle contraction and zonular relaxation allow the lens of the eye to become rounder or more convex. This increases the optical power of the lens and enhances the ability of the eye to focus at near distances. Accommodation can allow the eye to focus and refocus between near and far objects.
Presbyopia normally develops as a person ages, and is associated with a natural progressive loss of accommodation (sometimes referred to as “old sight”). The presbyopic eye often loses the ability to rapidly and easily refocus on objects at varying distances. There may also be a loss in the ability to focus on objects at near distances. Although the condition progresses over the lifetime of an individual, the effects of presbyopia usually become noticeable about the age of 45 years. By the age of 65 years, the crystalline lens has often lost almost all elastic properties and has only limited ability to change shape. Residual accommodation refers to the amount of accommodation that remains in the eye. A lower degree of residual accommodation contributes to more severe presbyopia, whereas a higher amount of residual accommodation correlates with less severe presbyopia.
Work is now underway on developing methods and devices for treating presbyopia. These treatments often seek to provide vision approaching that of an emmetropic eye. In an emmetropic eye, both distant objects and near objects can be seen using the accommodation of the eye. To address the vision problems associated with presbyopia, traditional treatments have included reading glasses and the like. Reading glasses add plus power diopter to the eye of an individual, thus allowing the eye to focus on near objects and maintain a clear image. Presbyopia has also been treated with bifocal eyeglasses, where one portion of the lens is corrected for distance vision and another portion of the lens is corrected for near vision. Although such approaches can provide clear vision when the eye is looking through the appropriate lens, other objects in the field of view may be distorted. Still further alternative treatments have been employed, including monovision (in which one eye is corrected for distance vision while the other eye is corrected for near vision) and the like. Many of these therapies have been successful for at least some patients, but none has been shown to provide ideal viewing capabilities for all patients throughout a wide viewing distance range.
In the field of refractive surgery, certain ablation profiles have been suggested for treatment of presbyopia. The goal of these presbyopia ablation profiles is often to increase the range of focus of the eye, rather than attempting to restore a combination. Many of these ablation profiles can provide a wider depth of focus, although in many cases with some compromise. U.S. patent application Ser. No. 10/738,358, filed on Dec. 5, 2003 and entitled “Presbyopia Correction Using Patient Data”, the full disclosure of which is incorporated herein by reference, describes promising approaches for treatment of presbyopia using laser ablation and other refractive correction techniques. Many of these proposed refractions are adjusted or tailored for a specific patient.
While the newly-proposed presbyopia treatment approaches show great promise, still further enhancements in the field would be helpful. In particular, presbyopia treatments may benefit from increased knowledge regarding the response of the eye to different viewing conditions. This may, for example, facilitate developing appropriate classes of treatment shapes through a better understanding of typical physiological changes to the eye when the patient changes between viewing at near and far distances. Improved devices for measuring the eye's response to changes in viewing distances may also help tailor or select appropriate treatments for a particular patient, or may be used to exclude certain patients from treatments which would be inappropriate and/or result in visual acuities that are less than may otherwise be available through alternative treatments.
In light of the above, it would be advantageous to provide improved devices, systems, and methods for measuring and/or diagnosing eyes. It would be particularly advantageous if these improved techniques facilitated developing and/or tailoring of refractive correction prescriptions for classes of patients or individual patients.